Systems and methods which use an interface for connection between the units are known in the prior art. These connections comprise one or more wires dedicated only to the transport of a specific signal allowing the synchronization. However, this solution does not allow a standard connection interface because it requires one signal more, one specific circuit more, one connection means more, and a specific protocol. Furthermore, the information conveyed by this buffered signal does not have the same latency as the Ethernet MAC frame on its interface. An Ethernet MAC frame is intended to mean a data packet transmitted by using the Ethernet local area network protocol. Specifically, the circuit in charge of managing the connection interface sends the signal directly, whereas the MAC frame has undergone several tens of offset clock periods. These systems therefore present a problem of synchronization of the signal intended to synchronize the message.
Systems and methods based on packet exchange are also known in the prior art. This transfer uses a standard connection interface dedicated only to transfer of the data. One example which may be mentioned is the IEEE1588 standard (known by the acronym PTP for “Precision Time Protocol”), which was proposed in 2002 to satisfy the constraints of the real-time methods employed in various technical fields. This standard proposes a very precise solution for synchronization of the clocks (this precision is within one microsecond) of a plurality of networked units. Since this standard is defined for the synchronization of a plurality of units distributed over a local area network, however, it presents a complex method. The complexity of this method is due in particular to the search for the device having the most precise clock in order to make it the master clock of the network. This complexity makes its use problematic in a unit having a low calculation capacity and with few memory resources.
It is therefore an object of the present invention to overcome these problems by providing a system and a synchronization method not having the need for one or more wires dedicated only to the transport of a specific signal making the synchronization possible, and having a low complexity.